Helmets are worn in sports and other activities to protect their wearers against head injuries. To that end, helmets typically comprise a rigid outer shell and inner padding to absorb energy when impacted.
Various types of impacts are possible. For example, a helmet may be subjected to a radial impact in which an impact force is normal to the helmet and thus tends to impart a translational movement to the helmet. A helmet may also be subjected to a rotational impact which tends to impart an angular movement to the helmet. The rotational impact can be a tangential impact in which an impact force is tangential to the helmet or, more commonly, an oblique impact in which an impact force is oblique to the helmet and has both a radial impact force component and a tangential impact force component.
A rotational impact results in angular acceleration of the wearer's brain within his/her skull. This can cause serious injuries such as concussions, subdural hemorrhage, or nerve damage. Linear acceleration also results if the rotational impact is oblique.
Although helmets typically provide decent protection against radial impacts, their protection against rotational impacts is usually deficient. This is clearly problematic given the severity of head injuries caused by rotational impacts.
For these and other reasons, there is a need for improvements directed to providing a sports helmet providing protection against rotational impacts.